1. Field of the Invention
The present invention is in the field of impellers. More particularly, the present invention is an impeller which reduces the audible high pitched noise generated in regenerative technology blowers.
2. Brief Description of the Prior Art
Regenerative blowers are non-positive displacement, high volume, low pressure devices that can operate as pneumatic compressors or vacuum pumps. A regenerative blower includes an impeller mounted directly on a motor shaft which is rotated at high speeds. The impeller typically has a large number of airfoil-shaped radial blades on its periphery. As the impeller spins, the blades pass an inlet port which creates a low pressure area and draws air (or other gasses) into the blower housing. A hollow, circular ring between the impeller blade tips and the housing wall acts as a compression space. The rotating impeller blades then use centrifugal force to impart motion to the air in order to accelerate the air radially outward and forward through the housing chamber as it follows the contours.
The “regenerative” principle takes effect as a certain amount of air slips past the tip of each impeller blade and returns to the base of a succeeding blade for re-acceleration within the compression space. Regenerations of the air within the blower housing are repeated and each regeneration becomes another “stage.” Each “stage” imparts more pressure to the air and creates a vortex. The pressure increase at each stage may be small, but the large number of stages allows for the incredible continuous operating pressures of the regenerative blowers.
When the vortex of air reaches a separator section at the outlet, i.e., the part of the blower located between the inlet and the outlet in which the annulus is reduced in size to fit closely to the sides and tips of the impeller blades, the air is stripped from the impeller and discharged from the blower. The discharged air is free of pulsation and the pressure or vacuum generated by the one or two spinning, non-contacting, oil-free impellers in regenerative blowers will be equal to the values obtained by many larger multi-stage or positive displacement blowers.
Regenerative blowers are available in many configurations and designed to meet specific applications and are used in a broad range of applications including, but not limited to, pneumatic conveying, sewage acceleration, vacuum lifting, printing presses, and aquaculture/pond aeration. Regenerative blowers have many benefits including simple operation, high reliability, minimal maintenance, a broad performance range, oil-free operation, and a generally low noise level.
Moreover, regenerative blowers often use one or two double-sided or “paddle wheel” impellers. This impeller design has twin vortices and is characterized by higher noise levels as the vortices are created at the inlet and merged at the discharge. The noise created by “paddle wheel” impellers is generally high pitched, and ways to reduce the pitch of this noise are therefore desirable.
Accordingly, it is desirable to have an impeller design that reduces the amplitude of the overall pitch of the noise emitted therefrom by creating several smaller “peaks” in the sound wave over a set period of time, instead of the standard design that has a single “peak” in the sound wave over that same allotted period of time.
While the prior art discloses many types of impellers, so far as is known, none of these assemblies, resolve these problems in a simple, effective and highly advantageous manner, as in the present invention.